I figured out that it was drastically slowing down queries, so I now pick only flags relevant to the query.
But if for example I don't pick EVERYTHING_REQUEST_DATE_MODIFIED then I can't retrieve the modification date through the results.
Do you have any clue on how to optimize the selection of flags for a query and still offer enough information in the results?

And by the way is there any reason why searching for creation date is so slow compared with other date queries?

About the scenario when the information is not indexed, is the time spent to gather data done on every such query?
And still about index information, in the added methods to your SDK I didn't see anything about ID3 tags and image data (width, height, bpp).